Microelectromechanical systems (“MEMS,” also referred to as “MEMS devices”) are a specific type of integrated circuit used in a growing number of applications. For example, MEMS currently are implemented as gyroscopes to detect pitch angles of airplanes, and as accelerometers to selectively deploy air bags in automobiles. In simplified terms, such MEMS devices typically have a very fragile movable structure suspended above a substrate, and associated circuitry (on chip or off chip) that both senses movement of the suspended structure and delivers the sensed movement data to one or more external devices (e.g., an external computer). The external device processes the sensed data to calculate the property being measured (e.g., pitch angle or acceleration).
Although they are relatively small, there still is a continuing need to reduce the size of MEMS devices and other types of integrated circuits. For example, in the cell phone industry, engineers often attempt to reduce the profile of internal application specific integrated circuits (ASICs) that have circuitry only. A reduction in the ASIC profile desirably can lead to a corresponding reduction in the overall size of the cell phone. To those ends, many in that field use conventional substrate thinning processes (e.g., backgrinding processes) to thin the substrates of many types of ASICs.
Undesirably, the prior art does not appear to have a similar solution for MEMS devices. Specifically, prior art substrate thinning techniques may damage the fragile MEMS movable structure. For example, prior art backgrinding processes (commonly used for integrated circuits without structure) require that the top side of the ASIC be secured to a supporting surface so that the bottom side may be exposed for backgrinding processes. The top side of a MEMS device, however, has the fragile MEMS structure. Accordingly, the MEMS structure would be crushed if backgrinding were used to thin the substrate of a MEMS device.